As one of the world's most critical staple crops, wheat (Triticum aestivum L.) requires continuous genetic improvement to ensure global food security. However, for a long time, research in wheat functional genomics and the progress of molecular breeding have been constrained by a core technical bottleneck: genetic transformation. Traditional wheat transformation methods suffer from low efficiency and severe genotype dependency—meaning they are effective only for a select few laboratory model genotypes (such as 'Fielder'), while yielding negligible results—or proving entirely ineffective—for the vast majority of commercial cultivars that hold significant breeding value.
In recent years, fusion protein technology involving Growth-Regulating Factors (GRFs) and their interacting partners (GIFs)—specifically GRF4-GIF1—has been demonstrated to significantly enhance plant regeneration capacity, offering hope for overcoming the genotype-dependent barriers to wheat transformation. However, the constitutive (continuously high-level) expression of such potent developmental regulators often leads to undesirable side effects (pleiotropy), such as abnormal plant development and reduced fertility; this has limited their practical application in breeding programs. Consequently, the key to achieving a revolutionary breakthrough in wheat genetic transformation technology lies in devising a strategy to cleverly harness the powerful regeneration-promoting capabilities of GRF4-GIF1 while simultaneously mitigating its potential negative impacts.
In September 2025, the team led by Sadiye Hayta at the John Innes Centre (UK) published a paper on the preprint platform bioRxiv titled "Controlling GRF4-GIF1 Expression for Efficient, Genotype-Independent Transformation Across Wheat Cultivars." In this study, they developed and optimized a highly efficient and robust Agrobacterium tumefaciens-mediated wheat genetic transformation system based on the GRF4-GIF1 fusion gene.
This research not only successfully extended transformation capabilities to several wheat cultivars previously considered "recalcitrant" (difficult to transform), but—more importantly—it ingeniously resolved the pleiotropic issues associated with GRF4-GIF1 overexpression through the introduction of tissue-specific promoters and an inducible gene excision system. This work provides a universal, efficient, and safe platform for wheat functional genomics research and precision breeding.
The research team first systematically evaluated the impact of a GRF4-GIF1 fusion gene—driven by a strong promoter (the maize ubiquitin promoter, ZmUbi)—on transformation efficiency across nine hexaploid common wheat varieties and several tetraploid durum wheat varieties. The results were highly encouraging: in all tested varieties, the introduction of GRF4-GIF1 significantly enhanced the regeneration capacity of callus tissue and boosted overall transformation efficiency. In the model variety 'Fielder,' transformation efficiency soared to 77.5%; in the important UK variety 'Cadenza,' efficiency reached 60%; and even in 'Borlaug 100'—a variety widely utilized in international wheat breeding programs—efficiency reached 40%. More importantly, this technology successfully overcame the transformation challenges associated with several winter wheat varieties (such as 'Skyfall' and 'Valoris') that were previously considered extremely recalcitrant to transformation using traditional methods, achieving transformation efficiencies of 16–20%. Similarly, the technology performed exceptionally well in tetraploid durum wheat, achieving an efficiency as high as 55% in the Italian variety 'Svevo.'
This series of results provides compelling evidence that GRF4-GIF1 technology can effectively overcome the genotype-dependency inherent in wheat transformation, thereby expanding the scope of genetic manipulation from a limited number of model varieties to a broad spectrum of elite cultivated varieties. However, the study also revealed that transgenic plants harboring high copy numbers of the GRF4-GIF1 gene exhibited varying degrees of reduced fertility—a negative effect that was particularly pronounced in certain varieties (such as 'Kronos'). This finding underscores the critical necessity of precisely regulating the expression of this gene.
Figure 1. Regeneration of wheat calli using the ZmUbi GRF4-GIF1 construct across different cultivars. (Hayta, et al. 2025)
To address the negative consequences associated with the constitutive expression of GRF4-GIF1, the research team devised an elegant solution involving the use of tissue-specific promoters. They replaced the ZmUbi promoter—which originally drove the expression of GRF4-GIF1—with the promoter from the maize phospholipid transfer protein gene (ZmPLTP). This specific promoter is characterized by its high-level expression primarily during the early stages of transformation—specifically within embryogenic callus tissue—while maintaining very low expression levels across most tissues of the mature, developed plant.
The experimental results perfectly validated this design concept: under the control of the ZmPLTP promoter, the GRF4-GIF1 construct not only exerted a powerful effect during the critical regeneration phase—thereby ensuring high transformation efficiencies (20% in the 'Fielder' variety and 23% in 'Kronos')—but also became "silenced" during the subsequent growth and development of the plant, thereby significantly mitigating adverse phenotypes. Transgenic plants utilizing this system exhibited tiller numbers, flowering times, and fertility levels closely comparable to those of non-transgenic controls, demonstrating normal growth and development.
As an alternative solution, the research team introduced a heat-inducible Cre/lox gene excision system to achieve the "post-use deletion" of the GRF4-GIF1 expression cassette. In this system, the GRF4-GIF1 gene is flanked by loxP sites, while the vector simultaneously carries a Cre recombinase gene driven by a heat-shock promoter (HvHsp17). Once plantlets had regenerated from the callus, a simple heat treatment (40°C overnight) was applied to induce the expression of the Cre enzyme, thereby precisely excising the GRF4-GIF1 gene fragment.
This "one-click delete" strategy achieved an excision efficiency of up to 73% in the 'Kronos' variety. In plants where GRF4-GIF1 was successfully excised, adverse phenotypes—such as excessive tillering—were significantly alleviated, and fertility was restored to normal levels. This "deploy-and-destroy" strategy provides a highly efficient pathway for generating "clean" transgenic or gene-edited plants that are free of residual developmental regulatory genes.
To further evaluate the advantages of the GRF4-GIF1 system, the research team compared it with WOX5—another morphogenesis gene previously reported to enhance wheat transformation efficiency. The results indicated that while WOX5 also improved transformation efficiency, the resulting transgenic plants exhibited more severe growth defects, such as stunted growth, enlarged grains, and spiral leaf growth. In contrast, the optimized GRF4-GIF1 system successfully achieved high transformation efficiencies while simultaneously better preserving the normal developmental trajectory of the plants.
Furthermore, this study successfully validated the feasibility of a co-transformation strategy: by employing two independent Agrobacterium strains—one carrying GRF4-GIF1 and the other carrying the target gene—comparably high transformation efficiencies were achieved. This approach is not only flexible and convenient but also allows for the easy elimination of GRF4-GIF1 in subsequent generations through genetic segregation, thereby offering significant practical advantages for actual plant breeding applications.
Figure 2. Phenotype of Fielder plants transformed with Wox5. (Hayta, et al. 2025)
Through systematic optimization and multi-variety validation of the GRF4-GIF1 technology, this study has successfully established a novel paradigm for wheat genetic transformation—one that is highly efficient, stable, and largely independent of genotype limitations.
The core contribution of this research lies in demonstrating not only the immense potential of GRF4-GIF1 in overcoming barriers to wheat transformation but also—through the introduction of sophisticated regulatory strategies such as tissue-specific expression and inducible gene excision—the ingenious resolution of potential pleiotropic side effects associated with the technology, thereby rendering it a truly safe and practical tool.
This work has vastly expanded the range of wheat varieties amenable to genetic manipulation, liberating cutting-edge technologies—such as gene editing—from their confinement to a few model varieties and enabling their direct application to elite commercial varieties worldwide. This will undoubtedly accelerate the pace of research in wheat functional genomics and pave the way for precision-designed crop improvement, holding profound implications for enhancing crop stress tolerance, nutritional value, and productivity.
| Cat# | Product Name | Size |
| ACC-100 | GV3101 Chemically Competent Cell | 100μL/tube |
| ACC-103 | EHA105 Chemically Competent Cell | 100μL/tube |
| ACC-105 | AGL1 Chemically Competent Cell | 100μL/tube |
| ACC-107 | LBA4404 Chemically Competent Cell | 100μL/tube |
| ACC-108 | EHA101 Chemically Competent Cell | 100μL/tube |
| ACC-117 | Ar.Qual Chemically Competent Cell | 100μL/tube |
| ACC-118 | MSU440 Chemically Competent Cell | 100μL/tube |
| ACC-119 | C58C1 Chemically Competent Cell | 100μL/tube |
| ACC-121 | K599 Chemically Competent Cell | 100μL/tube |
| ACC-122 | Ar.A4 Electroporation Competent Cell | 50μL/tube |
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